A great variety of prior-art methods of extracting phosphorus from slimes is a result of a complex structure of the slimes. Slimes are aqueous emulsions of phosphorus, said emulsions being stabilized with various emulsifiers of organic or inorganic origin, such as asphalt-resinous compounds, soot, finely dispersed mineral dust.
An aggregation stability of phosphorus slimes is characterized by the dispersity of phosphorus particles, the latter being dependent on the nature of the stabilizer. To stabilize less stable phosphorus emulsions, use is made of low-molecular hydrocarbons (calcium soaps), so-called "oils". The most stable slimes are stabilized with asphalt-resinous compounds; the higher the concentration of these compounds in the slime, the more difficult it is to extract phosphorus from slime.
The type of the stabilizer used depends, first of all, on the composition of the raw material being processed, the extent of its preparation, and the technology of phosphorus production.
The diversity of structural elements entering into the composition of the protective layers of phosphorus particles dictates a great variety of the reagents used for destruction of the structural elements. Among them are chlorinated hydrocarbons, carbon disulphide, pyrolysis resin, hexavalent chromium compounds in an acid medium, hydrogen peroxide in phosphoric acid.
An application of non-regenerable critical inorganic reagents in the process of phosphorus extraction from slime makes the process more expensive and contaminates the environment with toxic compounds.
Known in the art is a method of phosphorus extraction from slime by treating the slime with an organochlorine reagent in the presence of hydrogen peroxide upon heating. The mass ratio of the organic reagent and phosphorus in the slime is 8-10:1 (SU, A, 856976). The extraction of phosphorus from slime by this method is based on the extraction of organic stabilizers of the phosphorus emulsion with chlorinated hydrocarbons in the presence of an oxidizer. The use of large volumes of the extractants is the main condition for the extraction of the above stabilizers; this complicates the technological process and makes it more expensive.
Because of a partial hydrolysis of the hydrocarbons, which results in the formation of hydrochloric acid and enchances the corrosion activity of the reaction medium, corrosion-resisting equipment must be used.
This method makes it possible to extract phosphorus in high yield only when poorly stabilized phosphorus slimes are processed. This is determined by the nature of the extracting agent.
The slimes stabilized with asphalt-resinous compounds cannot be processed by this method.